Take whatever personal entertainment you like; laptop/tablet/phone/handheld console/book etc.
I had made sure my Switch was charged and got my Kindle ready, but for the one afternoon so far I just listened to podcasts and scrolled my phone.
My court had a bookcase with books and even a couple of jigsaw puzzles that the Jury Officer joked about showing an indication of how much waiting there can be.
Apparently there was wifi available, but there seemed to be limited power outlets in the small ‘waiting’ area we were in. The chairs were also not that comfy.
I realise all courts will be different regarding this though.